of Edinburgh, Session 1871 - 72 . 599 
Hence 
se = j (sn-<Sy) = j?s<. 
Introducing the hypothesis, obtained from considerations of Dissi¬ 
pation of Energy, ( Proc . Dec. 19, 1870) that 
we have 
<n = Kt, = ht, 
3j=^=(.K-h) (T« 6 -0, 
where T a6 is the well-known “neutral point.” 
Also 
E = (Jc a - h b ) (t - 0 (T^) , 
since it vanishes for t - t v the temperature of the cold junction. 
Now, if the neutral point be between such limits as 0° G. and 300° 
C., the exact determination of it is an easy matter; and this ex¬ 
act knowledge of it greatly facilitates the determination of 
dE 
dt ’ 
which cannot be very accurately found by drawing a tangent to the 
plotted curve. For if one junction he at t , the other at T a6 , we 
have 
“ K ) (^«6 “ O - 2 
E x and T ab -1 are easily measured on the experimental curve, and 
thus h a ~h b is found. The following values have thus been 
(roughly) calculated from observations. Where the neutral point 
was not reached, it is put in brackets. The unit for Jc a - h b is 3 or 4 
per cent, less than 
2 
10 5 
of the electromotive force of a good Grove’s 
cell. 
9 9 
99 
9 9 
99 
9 9 
9 9 
T 
Tea ~ kb 
T 
k 
a — kb 
- Cu (bad) 
265 C. 
- 0-00147 
Fe- A1 
(387) C. 
- 
0-00105 
- Cu (good) 
260 
- -00145 
„ - Arg. 
(1357) 
- 
•00045 
-Cd 
159 
- -00209 
Cu (bad) - Cd 
-(23) 
— 
•00081 
-Zn 
199 
- -00189 
„ -Zn 
-(146) 
— 
•00048 
- Ag 
235 
- -00151 
„ - Ag 
- (687) 
— 
•00006 
- Pb 
(357) 
- -00112 
,, (good) - Pb 
- (213) 
+ 
•00016 
- Brass 
(318) 
- -00127 
Pb-Cd 
-(74) 
- 
■00096 
-Pt 
(519) 
- -00063 
„ - Pd 
-(188) 
+ 
•00080 
- Sn 
(416) 
- -00094 
,, -Zu 
-(78) 
- 
•00060 
-Pd 
(1908) 
- -00029 
„ - Ag 
- (262) 
- 
•00026 
